Computer hard disc drives generally comprise an array of magnetic discs mounted to a spindle motor assembly. Data is written to, and read from, each magnetic disc by means of a read/write head located at the end of an arm which extends between the discs. Positioning of the arm is accomplished by means of a voice coil motor under the control of disc drive control electronics.
The array of magnetic discs is mounted to a hub of the spindle motor assembly. The hub is mounted for rotation with respect to a base of the spindle motor assembly by means of a bearing arrangement. In use, the hub is rotated by means of an electromagnetic motor. The bearing arrangement is expected to have a long, maintenance-free service life. In this regard, the amount of bearing fluid in the hydrodynamic bearing is chosen carefully; if there is too much bearing fluid in the bearing arrangement, some of it may leak out and contaminate other areas of the disc drive, while too little bearing fluid may result in the bearing arrangement seizing.
If the correct amount of bearing fluid is provided, it is important to ensure that leakage of bearing fluid from the bearing arrangement over the life of the motor is minimized. Any such leakage will have the consequence firstly of potentially contaminating the disc drive and secondly, of reducing the amount of bearing fluid below the ideal amount, potentially causing bearing arrangement failure.
Accordingly, it would be desirable to have a hydrodynamic bearing configuration in which bearing fluid leakage is reduced.